1. Field of the Invention
The invention relates to a method for producing a sheet pile wall from a number of sheet pile planks.
2. Description of the Prior Art
As is known, such sheet pile planks, on their longitudinal sides, are provided with jaw slots which are pushed into one another when the next sheet pile planks are driven into the ground. Thereby, a sheet pile wall is obtained which provides a good sealing, which may be important for a variety of reasons. The sealing may, for example, be necessary in order to separate one section of the ground in which the sheet pile wall is positioned from another section which may, for example, be contaminated. Such sheet pile planks are also used with harbour quays, where the sheet pile wall then has the function to retain the ground behind it and to protect it against the effects of the water.
For this reason, it is very important that the respective jaw slots interlock over the entire height of the sheet pile planks. In this connection, the client demands that the contractor demonstrate that the sheet pile planks have been arranged in the desired manner, that is to say maintaining the interlocking of the jaw slots. As the sheet pile planks are situated in the ground, certain measures have to be taken in order to make it possible to satisfy this requirement. In the past, various so-called jaw indicators have already been proposed, the purpose of which is to indicate to what extent the jaw slots indeed interlock over their entire height.
In accordance with a known jaw indicator, a sensor is positioned at the bottom of the sheet wall planks, at the jaw slot thereof. This sensor is connected to a measuring device on the surface of the ground via an electric wire, which has to extend over the entire height of the sheet pile plank. In order to protect the electric wire, a special tube is welded onto the sheet pile plank, through which this wire is pulled. As soon as the bottom end of the next sheet pile plank comes close to the sensor, this can be detected by means of the measuring device.
However, in practice, this known jaw indicator has proven not to work very well. First of all, the (delicate) sensor, which is situated at the bottom end of the sheet pile plank, may become defective during the operation of driving the sheet pile plank in question into the ground. Furthermore, the electric wire may be damaged despite the protection offered by the tube. A further drawback is the fact that, once the sheet pile plank has been removed from the ground, the tube is often partially loose and has to be removed before the sheet pile plank can be installed again.
With another jaw indicator, an indicator element to which a wire is connected is incorporated under the slot. This wire is pulled down into the ground with the sheet pile plank when the latter is driven into the ground. When the next sheet pile plank is then driven into the ground, this will push the indicator element out of the slot of the previous sheet pile plank. This can be detected at the surface by the fact that the wire of the indicator element can now be pulled up out of the ground. However, the drawback of this known indicator element is that the maximum depth over which the sheet pile plank can be driven into the ground is limited. At greater depths, the friction of the wire becomes so great that it can no longer be readily pulled out of the ground and, therefore, it is no longer possible to detect whether the indicator element has been removed from the jaw slot of the previous sheet pile plank.
It is therefore an object of the invention to provide a method for producing a sheet pile wall from sheet pile planks, in which it is possible to check in a simple and reliable manner whether the jaw slots interlock in the desired way.